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A. C. FULLER. TELEGRAPHY AND APPARATUS THEREFOR.

APPLICATION FILED SEPT. 22.19M-

Patented Sept. 16, 1919.

"HIM" IEGF avwwmcoz ATS P ALGERNON' CLEMENT FULLER, 6F WOBURN, ENGLAND.

TELEGRAPHY AN D APPARATUS THEREFOR.

Specification of Letters Patent. P t t d S t, 1 ug Application filed September 22 1917. Serial No. 192,806.

To all whom it may concern:

Be it known that I, ALGERNON CLEMENT FULLER, a subject of the King of Great Britain and Ireland, and residing at Signal speech to be Service Training Centre, Woburn, in the county of Bedford, England, have invented certain new and useful Improvements in Telegraphy and Apparatus Therefor, of which-the following is a specification.

This invention relates to telegraphy and more particularly to telegraph systems in A further object of the invention is to err-- able telegraphic signals and telephonic simultaneously carried over the same line, the signals and speech being entirely separate and distinct one from the other.

With the above obj ects in view theinvention consists in a telegraph system so arranged that two distinct paths or circuits are provided for the signal and voice ourrents, and in the provision of means for reventin the high frequency impulses rom pro uoing any appreciable inductive effect in the line.

In order that the invention may be readily understood, reference is had to the accompanying drawing, the single figure of which is a diagram of the electricalcircuits and apparatus employed at each end of the line. Such apparatus comprises both sending and receiving devices for the telegraphic signals and also a telephone set for carrying. on conversation, and as the equipment at every station is the same, a description of the one station illustrated in the figurewill suffice for all.

Referring to the drawing in detail, I have illustrated the apparatus as arranged for connection to a line conductor at a and connected to earth at b, although of course a com lete metallic circuit can be employed if pre erred.

1' and t designate the receiver and transbe audibly received in a telephone remitter respectively of the telephone set adapted foruse in the ordinary way while Z designates the usual telephone transformer comprising a primary winding m connected by a conductor 26 with one of the terminals p of the transmitter t, and a secondary winding is connected by conductor 2 with one of-the terminals 0 of the receiver a". The other terminal of the receiver is connected by a conductor 1 with the line binding post a while the other terminal of the transmitter is connected to earth.

c designates the usual telegraphic send- 1ng key and this is connected by means of a conductor 3 through the secondary la and Wire 2 to line, through the receiver 0", a choke coil d of high impedance being included in this connection by means of a conductor 1. From the back contact 9 of the key 0 extends a conductor 5 to the pivot point of an interrupter. This interrupter comprlses a pivoted armature h carrying contact springs 7 at its ends. One of said contact springs is adapted to engage a pair of independent contacts Sand 14, while the other contact spring is arranged to engage a similar pair of contacts 8' and 14. The

contacts 8 and 8 are connected together by a wire 9 and thence by a conductor 10 to a telephonic receiver 2', shown as of the head type. From theother side of this receiver extends a conductor v11 which connects with a common return wire 12. This extends through apparatus presently to be described to the ground wire 2. A condenser f is connected between the wires 5 and 12 by means of a conductor 30 so as to bridge the contacts 8 of the interrupter, such condenser being in parallel with the receiver 2'.

The interrupter above mentioned may be of an suitable type, either mechanical or electrlcal, its object being to break up the incoming telegraph signals into high frequency impulses so that they may be audible in the telephone receiver 2'. As shown, however, the interrupter is electrical and comprises a polarized armature h and a bi-' Th1s magnet.

- over a local circuit comprising conductors 21 and 22, switch 8 and contact 23.

Sending is done by means of an ordinary direct current battery which is indicated at m and when the sending key 0 is depressed, current flows from such battery over the Wire 33, wire 27, contact 28, key 0, wire 4, impedance coil d, wire 3, secondary k of the transformer, Wire 2, receiver r, Wire 1, and binding post a to line, the other side of the battery as bein connected to ground over the wires 34 an 2. The intermittent direct current forming the dots and dashes of the ordinary Morse code is not of sufficient frequency to be interfered with by the impedance coil 03. In other words, this sending current is substantially a direct current and therefore can readily pass.

through'the impedance coil.

With the above description it is thought that a full understanding of the invention will be had from an explanation of the operation of the system.

Telegraph signals, comprising intermittent direct current sent out from a sendingstation over the line, as above described, come in at a and flow over the wire 1 through receiver 1', wire 2, secondary 7c of the transformerl, wire 3, impedance coil d, wire 4;, key 0 and back contact g, wire 5 to interrupter armature k,- from whence the current passes, with the armature in the position shown in the drawingse to contact 8 and thence over wires 9 and 10 through receiver z, whence it passes over wires 11 and 12 to ground. Meanwhile, the switch 8 having been thrown over onto contact 23 for receiving, the interrupter device it is ener gized from the battery y over an independ ent local circuit. Beginning from one side of battery 3 this circuit includes wire 17, windings 16, wire 15 and contact 14, or. wire 20, windings 19, wire 18 and contact 14, (according to the position of the armature h) and thence from such armature over the wire 22,,c0ntact 23, switch 8, wire 21, back to battery. Thus the armature h is caused to vibrate continuously'at a comparatively high rate, thus breaking up telegraph signals coming in over the contacts 8 and 8' into a series of high frequency impulses, so that such signals become readily audible in the telephone receiver 2'. As long as the sending key at the distant station is depressed, current flows continuously through the line and through the choke coil d, thus keeping the condenser f charged, and at each oscillation of the armature k such condenser discharges through the telephone receiver 2'.

It will be particularly noted, however, that owing to the high impedance of the coil d, it is practically impossible for the impulses generatedby the interrupter k to pass back into the line, since these impulses are of such frequency as to be effectually choked back by the coil d. Therefore while these high frequency impulses are employed in order to affect the telephone receiver, the current in the line is practically a direct current and hence does not produce any inductive effects. In other words, the high frequency impulses for actuating the telephone receiver are confined by the coil (1 to the local receiving apparatus Telephonic conversation may be carried 7E5v on between any two stations equipped with my improved apparatus by means of the transmitter 25 and-receiver r in the usual way. The alternating voice currents coming in over the line pass through the receiver 1", and secondary k of the transformer, but are unable to traverse the impedance coil 03. They therefore pass to the' ground wire 2 over wires 31 and 32 in which is interposed a condenser 6. This condenser serves to prevent the passage of the telegraph signal currents over the path just traced. The use of such condenser therefore, in combination with the impedance coil d enables the direct telegraphic currents and the alternating voice currents to be transmitted simultaneously over the line and to be separated at the receiving station and caused to traverse separate paths. Thus telegraph messages and telephonic conversation can take place simultaneously and independently. The transmitter t is connected by means of wires 26 and z in a local circuit. including the battery as and the primary m of the transformer Z, whereby voice currents are induced. in the 100 secondary k of such transformer in the usual manner.

at the called station. To this end a contact 24 is arranged to be engaged by the switch 8 and is connected by a wire 25 with the wire 26. Another wire 35 connects the wire 22 with the wire 34 below the battery :12, a push button 9 being interposed in the wire 35. When it is desired to call a station and the push button 9 is depressed, a local circuit is established as follows: from the upper side of battery :0 over the wire 33 through the primary m of the transformer Z, wire 25, contact 24, switch 8, wire 21, battery 3 in series, windings of the interrupter h, wire 22 and wire 35 through push button q, back to the lower side of battery m. This local circuit with the two batteries in series produces a powerful pulsating current. through the primary m of the transformer and this in turn induces an alternating cur- 1% rent of the same frequency in the secondary 7a, which alternating current asses out to line over the wires 2 and 1 an receiver 7'.

\Vhen neither calling nor receiving telegraph messages the switch 8 may be swung over into dotted line position so as to stop the operation of the interrupter and thus prevent wasting the local battery 12 It sometimes happens that, owing ,to the extreme sensitiveness of the apparatus, the proper reading of messages is interfered with by stray earth currents or the like.

To obviate this difficulty, I provide means .for balancing the stray E. M. F. by means of a potentiometer device. This consists of a coil a connected at one end to the wire 2 and at the other end by means of a wire 36 to a 'pair of contacts 37 and 38 of a reversing switch w which is in turn connected with a battery '0. A second pair of contacts 40 and 41 are connected by means of a wire 3}) with the wire 2. The telephone receiver 71 and associated parts are connected by means of the wire 12 with the potentiometer slide 13 on which is adjustably mounted the contact 42. It will be seen that by means of the. reversing switch w an electromotive force from the battery 41 can be impressed on the line 2 in either direction and that by means of the adjustable slide and contact arrangement the value of such electromotive force can be made to exactly balance that due to stray currents and thus noises in the receiver 2' absolutely prevented.

What I claim is 1. Telegraphic apparatus comprising an interrupter for breaking up the received signal current, a choke coil interposed between the interrupter and the line,- a grounded conductor providing a shunt path to earth at a point between the interrupter and choke coil, and a condenser interposed in said" conductor.

2. In a combined telegraph and telephone system, a receiving station having two tele-.

plrone receivers, such receivers being connected permanently in series in the telegraphic signal circuit, an impedance coil and the secondary of a telephone transformer being also included in said circuit, and an interrupter device interposed insaid circuit between the impedance coil and one of said telephone receivers.

3. In a combined telephone and telegraph system, the combination with the usual telephone receiver, transmitter and transformer of means for eneratin 1n the secondary of the transformer a strong alternat ing current for calling a distant station, such means comprising a source of direct current and an interrupting device connected in series with the primary of said transformer.

4. In a combined telephone and telegraph system, the combination with the usual telephone receiver, transmitter and transformer, of an auxiliary telephone receiver, an electromagnetic interrupting device, means for connecting said device in circuit with a source of direct current and the primary of said transformer in order to generate in the secondary of the transformer a strong alternating current for calling puznposes, and means for causing said device to break up incoming intermittent telegraphic code signal current into high frequency impulses audible in the auxiliary telephone receiver.

5. In a comlbined telephone and telegraph system, the combination with the usual telephone set and transformer, of a sec. ond telephonic receiver, means. for breaking up the usual intermittent code signals coming in over the line into high frequency impulses audible in such second telephonic receiver, such means including an electromagnetic interrupter and a local battery for operating the same, a main battery for transmitting telegraphic signals and means for generatmg a strong alternating calling current in the secondary of the said transformer, such means including said main and local batteries connected in series with the primary of said transformer.

6. In a telegraph system, thecombination with a telephonic receiver and means for rendering the usual code signals audible in such receiver, of means for preventing stray currents from entering said receiver, such means comprising a potentiometer device, including a reversing. switch and source of current, connected between the receiver and the external circuit.

In testimony whereof -I have signed my name to this Specification.

ALGERNON CLEMENT FULLER. 

